Printing plate



. 10, 1935. E. s. BALLARD PRINTING PLATE Original Filed Deo IlllIlllllllllllilIIIHHHHHHINH retenes est. le, less erstes aesinet reperire einer Ernest s.. Ballard, Berkeley, Galli., assigner to' Standard Process Corporation, Qhicago, El., a corporation ol Delaware Original application December l2, 31927, Serial No. 239,388. Divided and this application @stoiber 2l, 1,931, Serial No. 570,22l

6 Claims.

This invention relates to printing surfaces and to a novel method of printing.

intaglio printing surfaces heretofore generally used have been prepared from half-tone photographic negatives of the matter to be printed. Such negatives are utilized in reproducing on sensitized carbon or equivalent tissue the image 'of the negative ol the matter to'he formed on the plate. 'Such tissue is transferred to a copper or similar cylinder or stu'tace and developed in the usuel marmer. Etching oi the gelatine resist results in e printing surface in which the high are represented by minute inlr re= ceiving cells. the middle tenes by larger cells and' the shedcws by still larger cells. The depth of such cells varies widely and the quantity of ink retained in the cells.' citer passage oi the doctor blade, varies correspondingly so thet the tone value of the printed matter is in very large meas ure dependent on the depth ci the cells.

This invention aims to improve the art ci printing by controlling the tone values solely by the area of the cells from which the ink ows to the surface being printed to the end that the inlr may becaused to :dow through the plate rather than applied to the cells externally as is custernary. A

Another primary object ci the invention is to produce a printing plate having a multiplicity of minute separate and distinct ducts graduated in area to produce tones and shadows through which or fromwhich the ink is supplied tothe material or surface being printed.

Further objects of the invention will appear as e. description thereof proceeds with reference to the accompanying drawing in which:

Figure l shows a view ot a portion of a plate, illustrating how the dots may be arranged therein to produce the desired lights and shades.

Figure 2 shows a magnied view of a portion ci a screen positive used in the production of the plate.

Figure 3 shows a similar view oi a portion of a screen negative employed in the method.

Figure 4 shows a longitudinal sectional view through a cylinder over which is arranged a printing plate embodying my invention.

Figure 5 is a transverse sectional view through the parts appearing in Figure i.

Like reference characters indicate like parts throughout the several figures.

Typographic and pictorial printing processes as now operated have one common characteristic in that the ink is applied to the printing form from without, either by ineens of distributing (Gl. idle-l2?) rollers passing over the printing forms or by reo volving in contact with the printing cylinder. 0r the printing cylinder, as inthe case ci intaglio machines, may revolve in a trough of ink, the

surplus inlr being removed romthe cylinder by a lexible steel scraper known as a doctor blade".

Applicationoi the inl. by exterior means in volves dimculties and complications, as well es waste of material and labor. Where a doctor blade is employed, the constant friction against the cylinder frequently damagesthe printing surs face.

This wearing of the printing surface is espe cially objectionable where large jobs are under way. The worn printing surface has to be replaced in the middle of the job, and there is no certainty that it will conform exactly to the initial surface.

This invention is intended to overcome all these troubles by bringing the inlr from behind the plate, and directly through it, using minute ducts or holes in the plate to allow a percolating eect to occur. These extremely small ducts are graduated in sise, where pictures are to be lill printed, and by virtue of these varied sizes pro- 25 duce shadows, half-tones and high lights in the printing process. Thus these ducts taire the place 'in the rate oi inl: flow as aiected by the frictional area. of the sides of vthe dot. The area ol the ducts varies but the largest must still be small enough so that the ink will be held theres in by capillary action and friction to the end that it will be transferred evenly from plate to the material being printed.

There are a number of ways oi carrying out the present invention but prefer to produce the 'novel printing plate as follows:

- Having selected a photograph, l place this on the copy board of a copying camera, and by means of the usual photographic operations produce a negative thereof, either on paper or on glass. Thus I obtain a photograph in negative form, the high llghtsof the original being represented by dark areas, the middle tones by less pronounced shades, and the shadows by white areas. It ls from this negative that I carry out the next operation, which will give a. screen .positive in which the high lights will Ahe represented by small opaque dots, the middle tones by larger which, however, do not overlap or touch in any part.

-represents a large shadow dot, formed bythe light action from the white areas of the negative,

. and progressively,.proceeding toward the right,

may be seen the middle tone dots 3, and high light dots l, the latter merely points, as compared with the shadow dot 2; This screen positive is produced as follows: The' negative copy of the original is placed before a camera in which a half-tone screen has been established at a suitable distance in front of a sensitive photographic plate. This distance is generally much less than in the usual half-tone operations, being preferably about one-half of that customarily employed in half-tone work. In the lens chamber reserved for stops as employed in the half-tone process I place a diamond-shaped stop with the sides parallel to the lines of the half-tone screen. With this 'stop in place, and by altering the distance of the screen from the sensitive plate, I readily determine a 'screen distance that, upon making the exposure,

gives a dot formation corresponding precisely to' the tone gradations of the original copy. 'I'hat is to say, small dots will appear as highlight dots, larger dts representative of the middle tones, and very large dots representative of the shadows. Further, if the exposure has been timed correctly, these large shadow dots will not be joined or connected in any part, but will be more or less diamond-shaped, and with parallel sides.

Referring to the drawing. shadow areas of Figure 1, illustrating a screen positive thus'produced will show that I have produced a grid of transparent area, isolating the l relatively large dots, and that proceeding toward the middle tones this grid becomes wider between dots, and the dots smaller. In the extreme high lights the grid has become very heavy and the lines correspondingly wide, with the intervening dots relatively small.

As a further provision for the control of tone gradation, I am able by screen adjustment, and in development of the sensitive plate, to make the relatively large dots very opaque, while rendering the small high light dots moreor less tra-nslucent, or, in the highest lights, absent entirely. This procedure, as will be explained later, is most important in making my process highly 'ilexible and useful for the purposes set forth.

lHaving produced my screen positive, as illustrated by Figure l, I nowproceed along one of two courses, according to the eiect that I desire' to secure. It I am seeking a precise and exact reproduction of the photograph copy, anddo not intend to alter largely the tone values thereof, I proceed as follows: l

I place the screen positive, shown in Figure 1, in a photographic printing frame, or in the socalled "step and repeat" machine, and print it down photographically on a sensitive plate, thereby transforming it into a negative. In this negative the diamond-shaped dots will appear as transparent areas and the surrounding grid as an opaque network. This formation is shown in Figure 3.

I- now proceed to sensitize a smooth metal plate, with a light lsensitive solution, of which bichromated glue; as commonly used in photoengraving, is an excellent example. However,

This screen positive, in which the dots are ap- Study of the there are numerous compounds of the kind, that can be used with equal success. Upon this sensitized plate I impose my screen negative, as indicated in Figure 3, and submit the whole to the action of light. After a suitable exposure the sensitized plate is developed in water. If bichromat'ed glue has been used, the glue that has not been acted upon by the light will wash away, leaving a dot formation corresponding to the transparent dot areas of the negative.' The plate is then heated until the glue dots are burned in or carbonized, rendering them similar to the enamel dots of a half-tone plate that has been prepared for etching, but with one important exception. Whereas, in the true halftone formation, the shadows will consist of large areas produced by overlapping dots, giving socalled solids, in my plate the. shadow dots will be found isolated by narrow lines of exposed metal, forming a distinct grid or mesh effect. 'I'he plate thus produced I style a "master plate. From it, as will be explained, I can produce an ininite number of printing plates of exactly the same size and printing value.

It will be appreciated that I have created a screen effect similar to that seen in screen intaglio,vbut with tone values determined largely by the size of the dot between the walls of the screen, rather than by the depth of the vcell itself. 'I'he advantage of this formation will be pointed out hereinafter. Y.

Referring again to the master plate, I proceed 'as follows:

The plate is rubbed over with a compound that will prevent adherence of any metal that may be deposited thereon. Wax may be used for this purpose, although there are various methods for accomplishing this purpose. Having so prepared thel plate, I insert it in an electroplating bath, suitably prepared for the metal that is to be deposited, and proceed to form a relatively thin coating of metal over the master plate. No metal will form over the,v enamel dots, which are non-conducting, but it will form rapidly over those parts corresponding to the grid of varying The master plate-may be returned immediately to the plating bath and another plate prepared forV strippln away. This operation may be con- /tinued indefinitely, making as many duplicated plates as required.

The stripped plate is now ready for'printing.

`It is preferably placed around a .hollow metal cylinder 5, the surface of which is perforated by many small holes 6, which are covered in turn by a porous blanket 1 ofsuitable material. It is over this blanket that the printing plate is secured, encirclingv the cylinder and closely fastened thereto by suitable gripping and locking devices I. i

Ink is introduced into the hollow cylinder. It quickly percolates through the porous blanket, and reaches the inner surface of the printing plate, filling the minute ducts. As the cylinder is Vset revolving, 'with paper passing between it and an impression roller, capillary attraction draws the ink through the ducts, and results in ly reducing it in order to create a partial vacuum.

. It will be readily apparent that by this means I have very complete and delicate control over the ink fiow.

The printing plate having minute ducts or passages for the ink may also be produced by reproducing by well known photographic methods the ducts in a resist applied to a thin metal plate so that the metal is exposed at the multiplicity of points at which the ducts areo be formed. The thin metal plate may then be etched in known manner, the etching being carried forward until ducts are formed extending completely through the metal at all exposed points.

Having described my method of producing 'a printing plate where a precise duplication of the original is required, I shall now describe an alternative method followed where a change in tone value or contrast is demanded.

Returning to my screen positive as shown in Figure 1, instead of transforming this into a negative, I proceed as follows: A piece of carbon tissue as commonly employed in the photogravure process is sensitized with potassium bichromate and dried in the usual manner. It is then placed in a printing frame beneaththe screen positive, and a print of the latter made upon the tissue. This action of thalight is continued until the gelatine has been rendered insoluble for a considerable depth around the large shadow dots, but without actually penetrating these dots, or creeping to any appreciable extent beneath them. At the same time, incursion of light will occur around the much smaller high light dots, and the gelatine beneaththese dots will be rendered more or less insoluble.

I now transfer my carbon tissue in the usual manner to a metal plate, develop in warm water, and dry. Inspection will show the areas corresponding tothe large shadow dots almost, if not entirely, devoid of gelatine covering, while in the high light areas considerable gelatine will be found at the bottom of the dots.

I now proceed to etch with a heavy solution of perchloride of iron, of 41 or 49 Baum. ".lhisv solution will readily penetrate the shadow dot areas, and etch corresponding depressions in the metal, 'out as the high light dots are approached the etching will cease, for the heavy perchloride will not penetrate the gelatine skin at the bottom of the high light depressions. Consequently, by resorting to a perchloride of slightly less density,

say 36 Baume I may etch the high light areas as see fit, stopping the action when I consider the area and depth of the dots sufficient. Thus I may control the relative contrast of my picture, regardless of the original.

With this etching completed, I Wash away the gelatine, and dry what is now a master plate,

save 4for one remaining operation. This consists in iilling in the etched depressions or cells of varying area with a non-conducting and acid resisting compound, of which many combinations are possible. Wax works very well, and if rubbed over the plate soon fills the depressions. .The

surplus may be readily polished from the surrounding surfaces. I now proceed as in the first operation, treating the plate in order that a deposited metal may not adhere thereto, and

plating thereon and stripping away the relatively 5 thin coatings as heretofore described.

Type matter in my new process is handled with the utmost ease, and in practically the same manner as pictures, although even more easily. A negative of the type matter is made, and between' 10 it and the sensitized metal plate, a transparent medium carrying a screen of narrow opaque lines is interposed. This gives a grid eiect throughout the type matter, as printed down upon the master plate, and the result is identical with the pictorial process save that all ducts for the type matter are of the same size, thus giving a uniform printing throughout.

With my method of supplying ink to the printing surface by small holes or ducts, graded as to size and arrangement to print the desired impression, and controlling the supply of ink through the openings by air pressure or the like, any desired amount of ink may be supplied to the printing surface, whereby to giveeither a'thinvor a 25 heavy coat to the printed matter. With other methods of printing, the amount of ink which the printing surface will take is restricted, and only one shade of printing can be produced with a given plate, except that the printed matter be run through the press a second or third time.

, This application is a division of my application Serial No. 239,388, filed December 12,1927.

The invention may be embodied in other specific forms without .departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced4 therein.

What is claimed and desired to he secured by United States Letters Patent is:-

l. A printing or stencil plate in which the printing areas consist of separate and distinctI dot-like openings "in the plate of various sizes to govern the tone value of the printing, the maximum dimension of any opening being smaller than the distance between the center of any two openings in the plate and in which non-printing areas completely surround each and every opening and isolate said opening from adjacent openings in the shadows as well as every. other part of the plate.

2. A printing or stencil plate comprising a metal structure having printing areas co'nsisting of separate and distinct dot-like openings in the structure of various sizes, adjacent openings in the shadows as well .as in. other parts of the structure being separated from each other and each opening being completely bounded by continuous and uninterrupted non-printing areas, the max- @5 imum dimension of any opening being smaller than the distance between the centers of any two openings in the plate, whereby the variations in the tone value of the printing are obtained by varying the size of said openings and the dimenim sions of said non-printing areas.

3.'.A printing or stencil plate consisting of a metal body'having non-printing areas in a single plane and printing areas formed 'by means oi separated and distinct dot-like openings as printing -areas in the same plane and printingv areas consisting of separate and distinct dotlike openings of various sizes formed in the plate from said plane, the larger openings correspondj ing in position to the darkest parts of the printing and being each completely separated from adjacent larger openings by a non-printing area, the maximum dimension oi' any opening being smaller than the distance betweenv the centersroi.' any two openings in the plate, whereby the variation in tone value of the printing is obtained by varying the size of said openings and the dimensions of the nonprinting areas that completely surround cachot said openings.

5. A printing plate consisting of. a metal body having non-printing areas formed by the plane of its surface, and printing areas formed by means of separated and distinct dot-like openings 'of various sizes formed in said plate, every dot-like opening being'completely isolated and 5 separated from adjacent dot-like openings by a non-printing area and having a maximum dime'nsionsmallerthan the distance between the centers oi' any two openings in the plate whereby friction and capillary action in said dot-like 10 openings mayl be utilized to control the even transfer of ink from 'said plate. l

6; A printing plate consisting of a metal body having non-printing areas formed by the plane of its surface, and printing areas formed by 15 means of separated and distinct dot-like openings of various sizes formed in said plate, .every dot-like opening being completely isolated and separatedi'rom adjacent dot-like openings by av non-printing area and having a maximum dimen- 20 sion smaller than the distance between the centers of any two openings in the plate, the nonprinting areas being arranged so as to be parallei to each other regardless of their width.

ERNEST S. BALLARD. 25 

